This invention relates generally to engine exhaust handling apparatus, and more particularly, to apparatus for noise abatement and catalytic treatment of internal combustion engine exhaust gasses.
In the burning of petroleum fuels in an internal combustion engine, hydrocarbons in the fuel and nitrogen and oxygen from the air used to combust the fuel combine to yield various oxides and nitrides, principally comprising carbon monoxide, carbon dioxide, nitrous oxide and nitric oxide. Waste materials in the fuel, such as sulphur produce other oxides such as sulphur dioxide. Additionally, some of the fuel passes into the exhaust partially combusted or uncombusted.
Some oxides are more harmful to human beings than other oxides. For example carbon dioxide may pose less of a hazard than carbon monoxide. In order to minimize the more harmful emissions, most larger internal combustion engines, particularly those used in automobiles are equipped with exhaust gas catalysts in their exhaust systems (xe2x80x9ccatalytic convertersxe2x80x9d) to convert less desirable oxides to more desirable oxides.
Automobiles generally have a fair amount of space available for both a catalytic converter and for noise abatement apparatus such as mufflers and resonators to suppress the noise ordinally associated with internal combustion engine operation.
Smaller engines in applications such as lawnmowers are significant generators of pollutants but in the past have seldom if ever been equipped with exhaust treatment apparatus, despite that for their size they often generate proportionately more harmful emissions. Reasons for this may include the lack of expensive and sophisticated engine management systems found in more expensive applications such as automobiles.
It is an object of the present invention to provide an efficient catalytic muffler design which lends itself to compact dimensions so as to be easily accommodated in internal combustion engine applications.
It is a further object of the present invention to provide such a compact catalytic muffler which also has noise attenuation capabilities to obviate the need for a separate muffler.
It is also an object of the present invention to provide a noise abating catalytic muffler design for small engine applications which is simple and comparatively inexpensive to produce and which lends itself readily both to O.E.M. and retrofit applications.
A catalytic muffler having at least one reactor bed, each bed having an array of discreet adjacent flow zones, the flow zones being interconnected by a series of passages for unidirectional flow of a gaseous fluid sequentially through each adjacent zone in turn from an inlet side of each reactor bed to an outlet side of the reactor bed. An inlet fluidly communicates with a first of the flow zones. An outlet fluidly communicates with the last of the flow zones.
The catalytic muffler may include a housing having a partition dividing the housing into a reactor side and a return side. The reactor bed may be housed within the reactor side. The adjacent zones may be defined by wall members extending between the reactor bed, the housing and the partition at the inlet and outlet sides of the bed. The passages may be defined by baffle members in the return side of the housing, the baffle members extending between the partition and the housing. The passages may fluidly communicate with respective of the flow zones through respective apertures extending through the partition.
The catalytic muffler may have two reactor beds spaced apart with inlet sides facing. A single inlet may fluidly communicate with both of the first zones and a respective outlet may fluidly communicate with each of the last zones.
The catalytic muffler may have two reactor beds spaced apart with outlet sides facing. A respective inlet may fluidly communicate with each of the first zones and a single outlet may fluidly communicate with both of the last zones.
A first of the passages may diverge in the flow direction to reduce exhaust gas velocity as it flows therethrough and a last of the passages may converge to increase gas velocity as it flows therethrough.
A last of the apertures before the outlet may include an adjustable flow restrictor for varying flow restriction through the catalytic muffler.
The first passage may diverge by an amount corresponding to an amount by which the last passage converges.
The reactor bed may be made up of two parts, namely an upstream part and a downstream part. The upstream part may bear a reducing catalyst and the downstream part an oxidizing catalyst.